The presence of refractile (R) bodies, potential toxin-delivery proteic structures able to stretch by biochemical influence, has been verified in some free living and endosymbiont bacteria, but the role and genomic context of reb genes responsible for its polymerization is not yet understood. RebB domain genes appear on genomes of proteobacteria, bacteroidetes and acidobacteria, generally displaying several contiguous duplications, but operon configuration exhibits varied forms and distribution. In organisms where the structures has been experimentally characterized, R-bodies required the presence of distinct reb family members to ensure polymerization. Non-homologous regulatory genes have been demonstrated, but their taxonomic distribution and domains have not been fully determined. The precise order of events guiding lateral transfer and duplications in rebs and neighboring genes also remains undefined. Applying methods of data analysis to sequenced genomes, we intend to explore the presence of reb homologs and identify new genes associated with R-body function, allowing the inference of their evolutionary history and the factors that steer their distribution. The core of our strategy will be the application of tools for conservated gene blocks, phylogenetic comparative methods and amino acid substitution correlation measures. Potential genes identified in this work will serve as candidates for experimental characterization in future essays, with interest for the possible presence of toxins and antitoxins.
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